The limit is 3 for 1-2-Free/Rent Rent Reward coupons, as there's only 3 coupon slots on the booking page. Regular Emerald Club days can be combined up to 7 iirc. The 3+1 trick wouldn't work as we'll be out on the road at the time we'd have to extend. It's a lot more likely to be a 4 day rental than a 3 so I'm probably just going to leave it at that.